1. Field of the Invention
This invention relates to a variable equalizer for making variable a frequency characteristic which, when the frequency characteristic of a transmission line has changed, is introduced into the transmission line in order to compensate for the change.
2. Description of the Prior Art
Heretofore, the Bode type variable equalizer has been often employed in case of a change in the frequency characteristic of a transmission line. This variable equalizer varies the frequency characteristics by varying the resistance value of a single resistor. The equalizer requires a dual network, so that whenever a capacitor is employed in the circuit, a coil becomes necessary. It is therefore unsuitable for fabrication in the form of an integrated circuit and for miniaturization.
Further, the prior art effects the variation of the frequency characteristic on the basis of feedback. In this connection, it is difficult to eliminate the phase shift between an input and an output irrespective of the frequency over the entire frequency range, especially in a high frequency portion.